1. Field of the Invention
This invention relates to derivatives of polyglycerols having at least three glycerol units which are ethers resulting from the reaction of polyglycerol with a proper proportion of a reactive oxirane-containing hydrophobe compound.
In particular, the reactive oxirane-containing hydrophobe material is a glycidyl ether resulting from the action of epichlorohydrin upon a hydrophobic alcohol. A straight-chain fatty alcohol containing 6 to 20 carbon atoms may be used, or a suitable material may be derived by oxyalkylating a lower alcohol, one that would not itself be hydrophobic, with a sufficient proportion of propylene oxide and/or butylene oxide being used to impart the necessary hydrophobicity.
2. Description of the Prior Art
The preparation of various polyglycerols, by condensing glycerol in the presence of an alkaline catalyst at temperatures such as 100.degree.-300.degree. Centigrade is disclosed in Babayan et al. U.S. Pat. No. 3,637,774. The patent goes on to teach the making of various partial esters or full esters of such polyglycerols for various purposes, such as gelling agents, lubricants, wetting and dispersing agents, etc. The reaction of partial esters with alkylene oxides to form adducts is suggested. Such esters are, however, subject to hydrolysis under alkaline conditions.
The reaction of organic hydroxyl compounds (including polyglycerol) with alkylene oxides is disclosed in Moore U.S. Pat. No. 2,253,723. The patent discloses the use of stannic chloride as catalyst for the reaction of an alkylene oxide with virtually any organic hydroxyl-containing compound. Stannic chloride is completely unsuitable as a catalyst for the making of products in accordance with the present invention. Moreover, the patent does not mention the fatty epoxides which are used as reactants to produce the products of the present invention.
Alkali-stable nonionic surfactant compositions are known which result from the reaction of a fatty alcohol with a lower glycoside, in a manner similar to that described in U.S. Pat. No. 3,547,828 or U.S. Pat. No. 3,772,269. In these patents, neither the hydrophilic group nor the hydrophobic group has any similarity to those used in our composition; furthermore, such compositions differ chemically from those of the present invention, in that the hydrophobe is joined to the hydrophile through an acetal or a hemiacetal linkage, which is not stable in acid media.
U.S. Pat. No. 3,932,532 discloses the making of nonionic surfactants by reacting 1,2-alkylene oxides containing C.sub.8 to C.sub.20 alkyl groups with a particularly purified polyglycerol containing 3 or more glycerol units. Its teachings can be distinguished from those of the present invention both on the ground that the particular purification process set forth in the patent is not necessary and on the ground that the patent does not make it obvious to those skilled in the art that with a glycidyl-ether approach, results substantially as good can be obtained with the use of starting materials which are more readily available and less expensive.
U. S. Pat. No. 3,719,636 teaches making nonionic surfactants by reacting, for example, C.sub.12 to C.sub.14 fatty alcohols with several moles of glycidol ##STR1## When glycidol condenses, it yields (in effect) glycerol units. Working with glycidol has the drawback that the glycidol is not easy or inexpensive to make and that it is difficult to prevent the glycidol from self-polymerizing.